This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Membrane adenylyl cyclases (mACs) play an essential role in signal transduction by converting ATP to cyclic AMP and are therefore important potential drug targets. The crystal structure of mAC in complex with the activating G protein alpha subunit has been solved by our group. With our collaborators in Regensburg, we have discovered a new class of 2',3'- substituted purine and pyrimidine nucleotide inhibitors. Systematic kinetic analysis of over 30 compounds in this family, have identified several highly potent inhibitors with Ki values in the sub-nanomolar ranges. Crystal structures of mAC bound to three ligands in this family have revealed a novel mechanism of binding that is distinct from that of typical ATP analogs. We have developed a pharmacophore model to design a prototype inhibitors that interact with distinct subsites within the enzyme. We plan to determine the structures of mAC bound to two of these designed inhibitors. A series of compounds based on forskolin will also be tested.